1. Field of the Invention
This invention relates to a novel mix/effects switch arrangement for television video signals. In addition, this invention relates to a novel mix/effects switching system employing such a novel mix/effects switch arrangement.
2. Statement of the Prior Art
U.S. Pat. No. 3,604,849, issued Sept. 14, 1971, describes a mix/effects system which accommodates television effects such as mixing, wiping, keying etc. on two video inputs applied to the system. Because the system can receive only two inputs, its range of performance is limited. Thus, it is not possible to go from a mix to a key, as this requires three inputs.
In order to increase the versatility of switching effects available, the mix/effects systems of the above patent have been arranged in circuit with up to three systems in tandem. In these arrangements, the first system is fed from either two video sources or a key and a video source. The output of the first system is fed to one input of a second system, and the second input to the second system is a second video source. The output of the second system is, in turn, fed to one input terminal of a third system whose second input terminal is connected to a third video source.
The difficulty with this arrangement is that each mix/effects system is separately controlled by a different control lever. In the control room, the operator is required to handle these various levers to create various effects under conditions of substantial pressure. Decisions have to be made speedily, and an error resulting from the selection of the wrong lever, or from moving the right lever in the wrong direction, can have noticeably undesirable effects.
In addition, connecting the mix/effects system into an arrangement for handling more than two inputs requires a substantial amount of hardware which is expensive, and which reduces reliability and increases maintenance difficulties.